I. Field of the Invention
The present invention relates generally to vehicle sensors.
II. Background of the Invention
Modern motor vehicles are equipped with numerous sensors that provide detailed information regarding the operation of the vehicle. This information may be displayed for a driver or it may be processed and provided to various vehicle control systems, for example, to determine the angular speed or angular position of a rotating part in the vehicle, e.g., a crankshaft or drive shaft. Sensed signals may thus represent the angular position or angular speed of the rotating part. These signals can be used in various control systems, e.g., an ignition system and a speed control system.
Many current vehicle sensors require an arc-shaped magnet that has radial magnetization. The arc-shaped magnet is mounted on a rotating component for generating a changing magnetic field when the component rotates, with the field being sensed by a sensor for outputting a signal representative of the speed and/or direction of rotation and/or position of the rotating component. These arc-shaped magnets are expensive to make because they require a large and expensive magnetizer. Nonetheless, radial flux, while expensive to establish in an arc-shaped magnet, remains desirable because it promotes a linear sensor output.
An arc magnet assembly that has a virtual radial magnetization includes plural discrete magnet segments which have axial magnetizations. The magnet segments are disposed side by side to form an arc. With this structure, a magnetic sensor positioned adjacent the magnet assembly generates a substantially linear magnetic sensor output when the magnet assembly rotates.
In a preferred embodiment, each segment is generally trapezoidal-shaped, and each segment can have a concave inner face and a convex outer face. Magnetic concentrators can straddle the sensor.
In another aspect, a device for sensing at least one parameter (such as speed, direction of rotation, or position) of a rotating component includes a magnetic field sensor and a magnet assembly generally forming an arc and being engageable with the rotating component for movement therewith. As set forth further below, the magnet assembly is established by plural discrete magnets and is juxtaposed with the sensor such that when the magnet assembly is engaged with the rotating component and moves therewith, the sensor generates a substantially linear output signal.
In still another aspect, a method for making an arc magnet having a generally radial magnetization includes providing plural magnet segments, with each having an inner face, an outer face, and an axial magnetization relative to an axis extending between the faces. The method also includes arranging the segments side-by-side with the inner faces forming a substantially continuous arc and with the outer faces forming a substantially continuous arc to thereby form an arc magnet assembly. The magnetic fields of the segments combine to establish a generally radial magnetization of the arc magnet assembly.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: